Technical Field
The disclosure relates to a phosphor, a fabricating method thereof, a method for regulating the crystal phase thereof and a method for changing the crystal phase thereof.
Description of the Related Art
In recent years, energy-saving and environmental-protection concepts have been a major concern. As new lighting sources, light-emitting diodes (LEDs) can solve the problems that cannot be conquered by traditional incandescent lamps or fluorescent lamps. Also, LEDs meet the requirements of low power consumption and environmental protection. Therefore, issues such as exploiting new energies and increasing energy efficiency have attracted public attention. Color LEDs have been used widely in colored lighting, displays, entertainment, and so on. The development of the electronic display industry has been the most rapid. It is believed that LEDs will play an important role in photoelectric element applications in the future.
So far, the development of white light-emitting diodes (WLEDs) has been the main developmental direction of LEDs globally. WLEDs have advantages such as small size, low heat radiation, long life, low power consumption, and vibration resistance. WLEDs solve the problems that cannot be conquered by traditional lamps.
One of the most common WLEDs used in the industry include blue LED chips accompanied by YAG phosphor (Y3Al5O12:Ce; Yttrium aluminum garnet). However, in order to remedy the red light spectrum which YAG phosphor (Y3Al5O12:Ce; Yttrium aluminum garnet) lacks, the process for the red light-emitting phosphor-added WLEDs has become a new issue. In general synthesis methods for red light-emitting phosphors, fluorides are co-crystallized by evaporating hydrogen fluoride (HF) at a high temperature. However, the operation of such methods is dangerous and the hydrogen fluoride (HF) has to be recycled subsequently.
Inorganic fluoride K2[GeF6] has three crystal structures, including a hexagonal phase with a P3m1 space group, a hexagonal phase with a P63mc space group, and a cubic phase with a Fm3m space group. Related studies indicate that K2[GeF6]:Mn4+ phosphors with a hexagonal phase with a P3m1 space group show a red light line spectrum in a range of about 600 nm to about 650 nm, but do not show a zero phonon line (ZPL) near 620 nm. The emission characteristics of K2[GeF6]:Mn4+ phosphors with a hexagonal phase with a P63mc space group are very similar to that of K2[GeF6]:Mn4+ phosphors with a hexagonal phase with a P3m1 space group. However, K2[GeF6]:Mn4+ phosphors with a hexagonal phase with a P63mc space group show a zero phonon line (ZPL). In previous studies, formulas were adjusted to make phosphors produce a zero phonon line (ZPL). However, so far, there is still no method using chemical recrystallization to control the crystal phase of phosphors and regulate the production of crystal phase change and zero phonon line (ZPL).
Therefore, a safe and fast method for fabricating a red light-emitting phosphor capable of increasing the color rendering index for WLEDs, a method capable of controlling the crystal phases of phosphors, and a method for producing a crystal phase change and a zero phonon line (ZPL) are needed.